Principal, Software Engineer (L5)

See yourself at Twilio

Join the team as Twilio’s next Principal Software Engineer.

About the job

This position is needed to raise the technical depth of the systems that continuously test, measure, and assure the quality of Twilio's global carrier connections, and the operational platforms that Super Network's operations depend on.

Every call and message Twilio makes crosses a carrier network we don't control. This team is how we know those connections are healthy. We monitor and test them continuously, worldwide, for both voice and messaging reliability, and we build what our operations teams use to act on what we find. Increasingly that means LLM agents troubleshooting carrier problems without a human involved — and that's the part we most want to push further.

Responsibilities

In this role, you’ll:

• Design and deliver major components of Twilio's carrier test and observability platform, covering active voice and messaging testing, quality scoring, and global test coverage.
• Build high-throughput data and alerting systems that turn the data into signals operations teams can act on without drowning in noise.
• Extend and harden our production LLM systems for automated carrier troubleshooting — expanding the classes of issue they resolve without human intervention, and owning the evaluation, observability, and guardrails that make autonomous action safe.
• Diagnose cross-boundary failures where test results, carrier behavior, and platform telemetry disagree, and establish the observability needed to tell those cases apart.
• Contribute to technical design and review across the team, mentor engineers, and help shape written standards that outlast any single project.

Qualifications 

Twilio values diverse experiences from all kinds of industries, and we encourage everyone who meets the required qualifications to apply. If your career is just starting or hasn't followed a traditional path, don't let that stop you from considering Twilio. We are always looking for people who will bring something new to the table!

*Required:

• 12+ years of software engineering experience, including significant time at staff or principal level working on systems at large scale.
• Deep expertise designing, operating, and debugging distributed systems that ingest and process high-volume time-series or event data in production, including alerting, anomaly detection, and failure isolation.
• Hands-on experience taking LLM-based systems to production and keeping them there: context and tool design, evaluation against real outcomes, cost and latency management, and the guardrails required when model output triggers real actions rather than just producing text.
• Strong proficiency in at least one backend language used at scale (Java, Go, Scala, or similar) and fluency with event streaming and cloud infrastructure (Kafka, AWS, Kubernetes).
• Ability to communicate complex technical trade-offs clearly in writing and to influence peers through design review rather than authority.

Desired:

• Experience with telecommunications, messaging, or voice systems
• Experience with active network testing, monitoring, or quality-of-service measurement.
• Experience with agentic systems that take action on live infrastructure, and with the evaluation practices that make that trustworthy. 

Location

 This role will be remote, and based in Ireland.

Travel 

We prioritize connection and opportunities to build relationships with our customers and each other. For this role, you may be required to travel occasionally to participate in project or team in-person meetings.

What We Offer

Working at Twilio offers many benefits, including competitive pay, generous time off, ample parental and wellness leave, healthcare, a retirement savings program, and much more. Offerings vary by location.